Module documentation for 0.1

This package provides a LongDouble type, being 80bits of x87 data taking up
96bits on i386 and 128bits on x86_64. On arm it is an alias for 64bit double.
It does not provide a CLDouble type usable for FFI without wrapping in Ptr,
this needs to be done by the compiler.
See https://ghc.haskell.org/trac/ghc/ticket/3353.